1. (

• enforce ,
• impose ,
• constrain

) compel to behave in a certain way; "Social relations impose courtesy"; "duty constrains one to act often contrary to one's desires or inclinations" ;

2. (

• restrain ,
• confine ,
• hold ,
• constrain

) to close within bounds, or otherwise limit or deprive of free movement; "This holds the local until the express passengers change trains"; "About a dozen animals were held inside the stockade"; "The illegal immigrants were held at a detention center"; "The terrorists held the journalists for ransom" ;

3. (

• stiffen ,
• tighten ,
• tighten_up ,
• constrain

) severely restrict in scope or extent; "tighten the rules"; "stiffen the regulations" ;